These studies will utilize organ cultures of embryonic rat and chick lung tissues to study extracellular matrix synthesis and the regulation of bronchial development. Microscopy autoradiography; biochemical analyses and radioimmune assays will be utilized to characterize the types and relative proportions of collagen, proteoglycans and basement membranes in developing lung tissues. Immuno-electron microscopy will also be utilized to identify the cells synthesizing the different extracellular matrix components. In addition, we will study the effects of oxygen levels, ion concentrations and various pharmacological agents on lung development. These studies will contribute to our understanding of the role of connective tissue proteins and environmental factors such as oxygen concentrations on the regulation bronchial morphogenesis in the developing lung.